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The Slowing of Light.

  1. Jan 2, 2016 #1
    Something that recently caught my attention was the slowing of light particles - and keeping them slow. Light naturally slows when passing through transparent mediums, it is only in a vacuum that light move at it's true speed. By passing light through a mask made of transparent liquid crystals length wise, which changed the shape of the photons themselves, a team of scientists were able to keep the photons slow. Though not by much, they were constantly slower than natural light with unshaped photons (when passed through the same medium).

    This concept is a completely new concept, so I'm not sure where this could lead. Do you have any thoughts/ideas/speculations as to what this could lead to in the future?
  2. jcsd
  3. Jan 2, 2016 #2


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    As weird as it sounds, it's definitely possible for a pulse of light to have a group velocity slightly below c.

    Consider a pulse of light made from shining a laser beam on and off.

    That pulse is expressible as a sum (integral) over a number of plane waves, each with its own direction, traveling at exactly c.
    However, since all these plane waves are not traveling in exactly the same direction, the component of the velocities of the plane waves along the direction of the beam will be slightly less than c.

    As a result, the beam as a whole has a group velocity slightly less than c (even in a vacuum).

    There are different beam shapes where this effect is (slightly) more noticeable, such as in higher-order Laguerre-Gauss beams.
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